Question:medium

The time period of a mass suspended from a spring is \( T \). If the spring is cut into three equal parts and connected in parallel. The same mass is suspended from these parallel springs, then the new time period of the mass will be

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Cutting spring $\longrightarrow$ stiffness increases. Parallel $\longrightarrow$ stiffness adds. Always track \(k\) carefully!
Updated On: Apr 22, 2026
  • \( \frac{T}{4} \)
  • \( T \)
  • \( \frac{T}{3} \)
  • \( 3T \)
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The Correct Option is C

Solution and Explanation

Step 1: Understanding the Concept:
The time period of a mass-spring system is determined by the mass and the stiffness (spring constant) of the spring.
A crucial property of springs is that the spring constant \( k \) is inversely proportional to its natural length \( L \), expressed as \( k \propto \frac{1}{L} \).
When a spring is cut or combined in different configurations (series or parallel), the effective spring constant changes, which in turn alters the time period of oscillation.
Step 2: Key Formula or Approach:
1. Time period of a spring-mass system: \( T = 2\pi \sqrt{\frac{m}{k}} \).
2. Spring constant for a part of a spring: If a spring of constant \( k \) is cut into \( n \) equal parts, the constant of each part is \( k' = nk \).
3. Parallel combination of springs: The equivalent spring constant \( K_{eq} \) is the sum of individual constants: \( K_{eq} = k_1 + k_2 + ... + k_n \).
Step 3: Detailed Explanation:
Let the initial spring have a constant \( k \). The initial time period is:
\[ T = 2\pi \sqrt{\frac{m}{k}} \dots (i) \]
The spring is cut into three equal parts. The spring constant of each individual part becomes:
\[ k' = 3k \]
Now, these three identical parts are connected in parallel. The new equivalent spring constant \( K_{p} \) is:
\[ K_{p} = k' + k' + k' = 3k + 3k + 3k = 9k \]
The new time period \( T' \) for the same mass \( m \) is:
\[ T' = 2\pi \sqrt{\frac{m}{K_{p}}} = 2\pi \sqrt{\frac{m}{9k}} \]
We can simplify this as:
\[ T' = \frac{1}{\sqrt{9}} \left( 2\pi \sqrt{\frac{m}{k}} \right) = \frac{1}{3} T \]
Step 4: Final Answer:
The new time period of the mass will be \( T/3 \).
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